It is known that safety signalling on bicycles is usually accomplished by an electric generator having a part frictionally engaging the side of a wheel whereby the rotational energy thus obtained is converted into electric energy to light a lamp or other lighting device. In other cases, the lamp may be lit by means of an electronic device using batteries (see, for example, U.S. Pat. No. 5,121,305 issued Jun. 9, 1992 to Deed et al.). Such device provides the periodical lighting of an optical radiation element, such as an electroluminescent diode, a filament bulb or a xenon tube. The efficient operation of such safety devices depends on a constant verification of the state of the batteries. Since children are most frequent utilizers of bicycles, it is noted that, often, they neglect to signal the necessity of replacing the batteries, thus resulting in a real danger for their safety. Also to be considered is the expense caused by the repeat acquisition of batteries, which results in a number of users to abandon the use of such devices. Also, some of the substances used in these batteries contain materials dangerous to the environment.
Lighting devices which do not require the use of batteries exist wherein magnets are used for supplying electricity to bulbs (see, for example, U.S. Pat. No. 5,128,840 issued Jun. 7, 1992 to Seki et al. and French patent publication No. 2,413,731 published Jul. 27, 1979 to Kumakura).
Japanese specification 63-107446 (Norio Akamatsu) of May 12, 1988 describes a lamp unit for bicycle wherein a magnet is directly rotated by a wheel and wherein a magneto coil, not in contact with the magnet, induces an electromotive force when the magnet is rotated and passes close to the coil. However, with this device, the lamp unit is only lit when the bicycle wheel rotates (or when the bicycle is used). Hence, when the bicycle is not moving for any reasons, no warning is effected and this may result in serious consequences, especially at night.